64
JOHN
P. SCHAEFER A N D TERRENCE J. MIRAGLIA
Pa1 n.m.r. a t 15-min. reaction time showed approximately equal amounts of ethyl hypophosphite (-37.1, --14.8, and +8.3 p.p.m.) and hypophosphorous acid (-28.8, -6.9, and +15.2 p.p.m.) with fairly large unidentified peaks a t -40.6, -34.9, and -19.4 p.p.m. In 12 hr. the ethyl hypophosphite peaks were seen to be increasing a t the expense of the others, and in 4 days the formation of ethyl hypophosphite was nearly complete. T h e rapid initial reaction rate and unidentified transient peaks suggest the possibility of an orthoester-hypophosphite ester intermediate species; as in the ketal reaction. This reaction mixture appeared to disproportionate more slowly a t room temperature than the orthocarbonate or orthoformate reaction mixtures. Butyl Hypophosphite.-Hypophosphorous acid (16.3 g., 0.25 mole) and butyl orthoformate (60.4 g., 0.26 mole) were combined a s above. The temperature dropped to T o and n.m.r. showed about 9OqG conversion after 30 min. a t room temperature and complete conversion after 3 hr. The reaction mixture was evaporated a t 0" and 0.2 m m . in a rotary evaporator for 2 hr. giving 43.8 g. of clear, colorless residue. This weight corresponds to a 6976 solution of butyl hypophosphite in its reaction by-products. Identification was by n . m . r . (Table I ) . Usual Mixing Procedure.--Most reactions for which separations were not anticipated were carried (Jut in 5-mm. n.m.r. sample tubes. By forcing the open end of the tube into the crystalline acid and tapping the resulting plug of acid t o the bottom of the tube, the very hygroscopic acid could be transferred and weighed with very little absorption of atmospheric moisture. The organic reactants were dropped in through a capillary pipet while weighing, arid mixing u-as effectively accomplished with an oscillating vortex mixer. In this manner, reactions could be observed with n.m.r. within about 4 min. of mixing the reactants. Methyl 1-Hydroxy-1,l-dimethylmethy1phosphinate.-In the above manner, 0.444 g. (0.00673 mole) of hypophosphorous acid
[COSTRIBCTION FROM
THE
VOl. 86
and 1.400 g. (0.0136 mole) of acetone dimethyl ketal were combined. At 7-min. reaction time, P3l n.1n.r. showed methyl hypophosphite peaks about twice as large as peaks of unreactetl x i d . Little change occurred in a n additional hour. After 3 days, roughly 7.5cic of the phosphorus was coriverted t o phosphinate, but the remaining methyl hypophosphite peaks were still a b m t twice as large as the acid peaks. After 20 days, conversion to phosphinate was complete. T h e reaction product was evacuated a t room temperature, giving a clear, colorless residue of fairly pure phosphinate. Calcd. for C ~ H I I O J PC: , 34.8; H, 8.0; P, 22.4. Found: C , 33.9; H , 8.3; P , 22.2. €'3 x1.m.r.: doublet a t -33.6 and -56.3 p.p.m.; J P - =~
